Investigating the role of EZH2 as a therapeutic target in colorectal cancers

摘要 多梳抑制复合体2(PRC2)是一种高度保守的发育调节因子，它维持 通过动态沉默参与分化的关键基因来实现细胞同一性。EZH2的变化，催化 甲基转移酶已被证明在许多癌症中起驱动作用。激活EZH2中的突变有 在黑色素瘤和淋巴瘤等癌症亚群中被检测到。然而，在大多数实体肿瘤中，EZH2 更常见的是过度表达。在晚期肿瘤中，EZH2的表达水平逐渐升高，并已 在功能上被证明可以促进前列腺癌的转移。然而，EZH2在其他固体中的作用 肿瘤，包括结直肠癌(CRC)还没有得到充分的研究。具体来说，EZH2是 在78.5%的结直肠癌中过度表达，其表达似乎与患者的生存呈负相关。我们 假设EZH2可能是一个有吸引力的治疗靶点，尽管它在结直肠癌中的作用和靶点是 未知。结直肠癌是全球癌症死亡和晚期转移性疾病的主要原因之一。 仍然无法治愈。因此，对于结直肠癌的治疗，尤其是那些患有结直肠癌的患者，仍有大量未得到满足的临床需求。 激活KRAS中的突变。许多针对经典致癌激酶的药物都是无效的治疗方法，如 单一药物，如治疗KRAS突变实体瘤的MEK抑制剂。因此，一种方法是 开发更有效的联合疗法，可能会增强细胞对MEK抑制剂和/或 防止抵抗。在一系列研究中，我们的实验室开始探索基于EZH2抑制剂的联合疗法 在各种实体肿瘤中。有趣的是，我们发现EZH2抑制剂在以下情况下经常有效 与针对特定肿瘤类型中的其他关键致癌途径的药物相结合，如在乳腺和 前列腺癌。我们假设，共同靶向EZH2以及关键的致癌途径可能导致 通过在蛋白激酶水平和细胞外抑制关键致癌信号协同杀伤大肠癌细胞 转录水平。我的初步数据显示，EZH2和MEK抑制剂的组合起作用 杀死KRAS突变的CRC，这为治疗这种晚期疾病提供了一种新的方法。我提议发表以下讲话 在将联合疗法转化为临床之前，有几个基本的开放式问题，例如 作用机制，使肿瘤对治疗有反应的细胞内在因素，以及药物是否 组合在体内临床前和生物学相关的环境中起作用。在目标1中，我建议确定假定的 通过对敏感的EZH2/MEK抑制剂进行基因组分析来决定其敏感性的生物标志物 以及耐药细胞系。在目标2中，我将通过获得染色质的全局视图来阐明其作用机制 和基因调控，我将在结合后确定在结直肠癌中调节的关键PRC2靶基因 治疗。在目标3中，我将测试以EZH2为基础的联合疗法在体内异种移植模型中的疗效。 CRC。总之，这些发现将为基于表观遗传学的联合疗法建立一个新的范例 目前无法治愈的晚期疾病。

Abstract The Polycomb Repressive Complex 2 (PRC2) is a highly conserved developmental regulator that maintains cellular identity by dynamically silencing key genes involved in differentiation. Alterations in EZH2, the catalytic methyltransferase, have been shown to play a driving role in many cancers. Activating mutations in EZH2 have been detected in a subset of cancers, such as melanoma and lymphomas. However, in most solid tumors, EZH2 is more commonly overexpressed. EZH2 expression levels progressively increase in advanced tumors, and has been functionally shown to drive prostate cancer metastasis. Nevertheless, the role of EZH2 in other solid tumors, including colorectal cancers (CRC) has not been sufficiently explored. Specifically, EZH2 is overexpressed in 78.5% of CRC, and its expression appears to inversely correlate with patient survival. We hypothesized that EZH2 could be an attractive therapeutic target, although its role and targets in CRC are unknown. CRC is the is one of the leading causes of cancer deaths worldwide, and advanced metastatic disease is still incurable. Thus, there is a significant unmet clinical need for treatments for CRC, especially those with activating mutations in KRAS. Many drugs that target classic oncogenic kinases are ineffective therapies as single agents, such as MEK inhibitors for KRAS mutant solid tumors. Therefore, one approach has been to develop more effective combination therapies that might enhance the sensitivity of cells to MEK inhibitors and/or prevent resistance. In a series of studies, our lab began exploring EZH2 inhibitor-based combination therapies in a variety of solid tumors. Interestingly, we have found that EZH2 inhibitors are frequently effective when combined with agents that target other key oncogenic pathways in a given tumor type, such as in breast and prostate cancer. We hypothesize that co-targeting EZH2 along with key oncogenic pathways may lead to cooperative killing of CRC cells by clamping down on crucial oncogenic signals at both the kinase level and the transcriptional level. My preliminary data demonstrate that a combination of EZH2 and MEK inhibitors cooperate to kill KRAS mutant CRC, which reveal a novel approach for treating this advanced disease. I propose to address several essential open-ended questions before translating a combination therapy into the clinic, such as the mechanism of action, the cell intrinsic factors that render tumors responsive to treatment, and whether the drug combination works in an in vivo preclinical and biologically relevant setting. In Aim 1, I propose to identify putative biomarkers that dictate sensitivity to EZH2/MEK inhibitors by conducting genomic analyses between sensitive and resistant cell lines. In Aim 2, I will elucidate the mechanism of action by obtaining a global view of chromatin and gene regulation, and I will identify critical PRC2 target genes that modulated in CRC after combination treatment. In Aim 3, I will test the efficacy of EZH2-based combination therapies in in vivo xenograft models of CRC. Together, these findings will establish a new paradigm for epigenetic-based combination therapies for advanced diseases that are currently untreatable.